Method of producing foamed construction materials

ABSTRACT

An improved article made of foamed glass or similar materials and method of manufacture is disclosed. Thus, a construction panel may be formed to bear weight, withstand weather and take reasonable impact and abuse, because of a tempered outer skin supported inside by a skeletal network of solid poreless material formed about low density pockets of substantially constant size and frequency. 
     These panels are made by continuous pulling of the panels through a heat controlled mold in contact with the surface skin from a continuously fed molten mass into which is injected from the bottom size and frequency controlled foaming agents or gaseous bubbles which rise in the molten mass to a position where they are frozen in place.

TECHNICAL FIELD

This invention relates to a load bearing foam article such as glassconstruction panels and methods of manufacture thereof including theintroduction of gaseous bubbles of controlled size at predeterminedrates into molten materials for freezing in place to providepredetermined foam characteristics of uniform cell size and density.

BACKGROUND ART

The art of producing foamed metal, ceramic or glass articles is highlydeveloped. Many and various techniques are available for using foamingagents to produce a continuous output product in the form of a pipe orpanel.

U.S. Patents representative of this art include:

U.S. Pat. No. 2,937,938--Fiedler et al.--May 24, 1960;

U.S. Pat. No. 3,473,904--Kraemer et al.--Oct. 21, 1969;

U.S. Pat. No. 3,527,587--Velev et al.--Sept. 8, 1970;

U.S. Pat. No. 3,574,583--Goldsmith--Apr. 13, 1971;

U.S. Pat. No. 3,607,170--Molesak--Sept. 21, 1971; and

U.S. Pat. No. 4,124,365--Williams et al.--Nov. 7, 1978.

When the output product is in the form of glass sheets or panels,various skin characteristics and shaping operations can be achieved bytempering processes in the drawing, shaping and cooling operations asrepresented for example by U.S. Pat. Nos. 4,046,543--Shields--Sept. 6,1977 and 4,092,141--Frank et al.--May 30, 1978.

Other techniques are known in processing glass or foam which include theagitating of the molten materials and the removal of bubbles from themolten glass before further processing. U.S. Patents representative ofthis art are U.S. Pat. Nos. 3,826,303--Jorema et al.--July 30, 1974;3,960,532--Lazet--June 1, 1976; and 3,628,937--Schott--Dec. 21, 1971.

The latter patent also provides a method of forming foamed glass panelsby introduction of gaseous bubbles into molten glass.

Although such patents as Goldsmith U.S. Pat. No. 3,574,583, abovementioned, recognize the insulating value of foamed glass and glassblocks or bricks are well known as construction materials, there hasbeen a deficiency in the art in producing any long wear glass buildingmaterial suitable as a building panel that will give long life withoutprotective coatings when exposed to atmosphere as glass does and yethave foam light-weight insulating properties. Further building materialrequirements not found in foamed glass products of the prior art areweight bearing strength, fracture, crack and shatter resistance toimpact.

It is therefore a general object of this invention to improve the stateof the art by providing versatile foam articles which can be used aslong-life load-bearing construction materials suitable for exterior usewith insulation properties, and methods of manufacturing such articles.

Further objects, features and advantages of the invention will be foundthroughout the following description, claims and accompanying drawings.

DISCLOSURE OF THE INVENTION

A foamed article provided by this invention is typically a glass,ceramic or similar metallic foam having a tough tempered poreless skinthat resists shattering and cracking and serves as a decorative wallresistant to atmospheric corrosion. The foamed interior providesinsulating properties, light-weight and low energy-material cost, andfurthermore is constructed to produce bearing weight characteristics andto further resist shattering or cracking into and through the article.The article is characterized by uniformly distributed low densitypockets of controlled size and pattern within an outer tempered skin toproduce the desired characteristics by means of producing a skeletalstructure of poreless material with dispersed random paths surroundingthe lower density pockets to prevent any common pathway through thearticle that can support a fracture line through the article whileproviding a bearing support strength through the poreless skeletalconfiguration.

The articles are made by introducing gaseous bubbles or foamingparticles of standardized size and controlled frequency into the moltenmaterial to be frozen therein as the molten material hardens in thecooling process, while the skin surface is being formed, hardened andtempered preferably in a temperature controlled mold against which theskin surface is sometimes moved continuously. The preferred method offoaming the material is to introduce gaseous bubbles of controlled sizeand frequency into the bottom of the molten materials to rise thereininto a nestled pattern, then hardened. The gas may be of a characterthat chemically treats the pocket surfaces for strength or otherproperties and alternatively the gas or other low density pocket may beformed by introduction of controlled size and frequency foaming agents,salts, etc.

Other more detailed aspects of the invention will be found throughoutthe following description.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a fragment view in perspective of the foamed article providedby this invention in the form of a typical sheet or panel that could beused as a weight bearing construction member;

FIGS. 2 and 3 are respective increasing enlargements of portions of thepanel of FIG. 1 illustrating the interior low density pocket pattern andsurrounding skeletal network of the foamed articles provided by thisinvention;

FIG. 4 is a diagrammatic view, in elevation and partly in section, of areservoir supply of molten materials used in forming the foamed articlessupplied by this invention;

FIG. 5 is a diagrammatic elevation view, partly in section, of a foamingmechanism for producing panels in accordance with this invention;

FIG. 6 is a fragment perspective view of a foam construction memberhaving integral offset longitudinal support members made in accordancewith the teachings of this invention;

FIG. 7 is a diagrammatic elevation view, partly in section, of amechanism for forming and foaming the construction member of FIG. 6;

FIG. 8 is an elevation diagrammatic view, partly in section, of a systemafforded by this invention for producing foamed panels;

FIG. 9 is an elevation diagrammatic view, partly in section, of apreferred molten material feed system afforded by this invention; and

FIG. 10 is an elevation diagrammatic view, partly in section, of analternative system for forming foamed articles afforded by thisinvention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

A foamed article such as a construction panel 11 made in accordance withthis invention has features shown in FIGS. 1 to 3. A toughened, temperedskin 12 together with a foam 13 interior not only presents an outersurface that is cosmetically good but which withstands deterioration inthe weather and environment. The toughened tempered skin 12 and interiorintegral poreless skeleton structure 14 with interspersed randomlypositioned pockets 15 of low density such as gas bubbles provides astructure that will produce a complete load bearing structural modularwall, floor, ceiling and roof section including a decorative texturedand/or colored finish ready to assemble into a finished house orbuilding that is maintenance free and requires no paint.

In FIG. 2 the showing of skin 12 is diagrammatical to indicate atempered tough surface, but as seen in FIG. 3 the solid poreless glassor similar material 14 is integral throughout the panel forming a solidrandom patterned skeleton of high strength material. A preferredtoughened skin thickness obtained by drawing a panel out of a mold overa temperature gradient with the skin in contact with the mold is in theorder of 0.4 to 0.7 cm (1/64 inch to 1/4 inch) thick. Consider, forexample, a force or weight bearing on the panel 11 from an angle shownby arrow 18. This force will be distributed among various paths in threedimensions in the structure through the skeletal structure of porelessmaterial 14 surrounding the low density pockets 15 thus giving anunexpectedly strong bearing weight for a foam product, and will standimpact without fracture or travelling cracks as so common in its familycousin, glass plate. Similarly the forces of a localized impact such asstriking with a hammer at 17 will of course fracture and crush the localsurface region directly under the hammer which will possibly crush thefirst two or three layers of bubbles causing a localized face spall andthe balance of skeletal material quickly disperses the internal stressesand the bubbles prevent the spreading or growth of crack or shatteringand for the same reason offer a substantial degree of resistance tosound penetration. Such impact damage can usually be easily repaired. Inorder to attain this impact resistant property the article need have askin of the same material as well as controlled size pockets ofsubstantially uniform generation and/or distribution frequency (althoughrandomly placed individually) to arrange themselves into a well-orderedmatrix skeleton. For variations of raw materials insulating qualities,strength, weight, and other product characteristics, the density andbubble size will be varied.

These articles are made in a preferred manner by the process which isexemplified by the manufacturing equipment of FIGS. 4 and 5. The moltenglass reservoir 20 holds the raw materials which are obtained from anexternal furnace and entered by way of stream 21 through funnel 22. Thereservoir may have suitable metallic walls 23 appropriately heated byheaters 24, 25, 26, etc. A level control gage 27 assures an appropriatelevel of molten material to establish a pressure head and performs othercontrol functions later discussed. The molten material shall typicallybe referred to as glass, which includes various compositions, slags andchemicals, but could be plastic, metallic or ceramic in nature as forexample, aluminum, zinc or the like as shown in U.S. Pat. No.2,434,775--Sosnick--Jan. 20, 1948. Further desirable controls are thebutterfly valve 27 and the drain cock 28 so that flow in the outletpiping conduit 29 can be controlled. While other sources of moltenmaterials may be used, this simple reservoir system can be connected forproducing the process afforded by this invention with the configurationshown in FIG. 5 to bottom feed the molten glass into the verticallydisposed mold 30, 31 at a head pressure maintained at a level shown ongage 27 as effected by float 27A.

Thus, panels 11 are drawn from the mold 30, 31 by means of rollers 32-35and cut to proper length by saw 36 rotated on shaft 37. A sonic or X-rayinspection device illustrated by blocks 38, 39 will assure properdensity of the throughput materials 11A as they are drawn out of themold 30, 31 by the rollers 32-35 continuously with the surface skin incontact with the inner walls of mold 30, 31. Controlled cooling andtempering is further effected by cooling coils 40, 41 which may beserially connected or form any desired network establishing curingtemperature during continuous withdrawal. Thus, the molten materialswill harden in a form somewhat as shown by contour 42. To lubricate themold surface, the asbestos wick structure 45 for example is used with alubricant reservoir 46 that can be filled at inlet 47.

The manifold 50 protrudes into the molten material mass 51 at the bottomof the mold to eject under careful control bubbles or pellets 52 thatrise within the molten material into the hardening region 53 thereby toserve as a foaming agent to convert the molten material into a foam massin the regions enclosed by the skin which first hardens against thewalls of the mold 30, 31 as encouraged by the cooling coils 40, 41.

It is critical that the frequency and size of the foaming gaseousbubbles or pellets be carefully controlled to give the product thedesired characteristics hereinbefore set forth. Thus, the manifold 50 isconnected to a supply line 55, a pump or feeder device 56 and adispenser 57 that works into the manifold 50. The manifold may have anozzle as a dispenser in the case of gaseous bubble foaming agent, ormay have a pellet ejecting mechanism in the case of release of a salt orother chemical foaming agent.

The thickness of the skin 13 is determined by the relationship of thetemperature of the surface of the mold, die or forming device to thearticle 11 just before and during the time the article is solidifying.This is also the point in time where the bubbles 52 are moving towardthe wall of mold 30, 31. The colder the mold wall forming surface 30, 31is compared to the article 11, the thicker will be the skin 12.Smoothness of the skin 12 is determined by the smoothness of the formingsurface and the type lubricant used, if any.

Bubbles 52 are filled with air or gas or a mixture of gases to serve asthe foaming agent. Their size is determined by a number of differentvariables such as the size of the injecting hole or holes in a nozzlearray, the pressure at which air or gas is injected, and the pressuredifferential between air or gas in the bubble 52 and the molten material51 before the point of solidifying or crystallization. There are anumber of different gases that can be used to form bubbles 52. Apreferred one to use is the lightest one that will not unfavorablychange the properties of the material forming the article 11. Air is thecheapest and best if all other factors are favorable. However, certainkinds of gas might be preferred to alloy with the material or otherwiseto improve the properties of finished product. For example, but notlimited to this example, gas might treat the material 14 at the pocket15 surfaces to make a stronger article, or to make the product have adifferent coloration.

It is most desirable to have the foaming air or gas as cold as possible.In fact, the colder the better because this has the effect of formingchilled surface around each bubble 52 thus reducing chances of bubbles52 running together and making larger undesirable pockets 15. It wouldalso help in keeping bubbles 13 the same size and serves to cool theinterior of the article 11.

It might be desirable under certain conditions that certain chemicals ortheir compounds be mixed with molten material 51 before it is foamed ormixed with foaming gas agent to act as catalysts or to improve theproperties of the article 11 or to color it. If it is desired thesechemicals may be mixed with the air or gas before it is injected intomaterial to be foamed.

It should be understood that method shown and explained is capable offoaming many kinds of materials into many shapes, and each might havemany mixing combinations to make different densities. Therefore, itwould be impossible to describe exact temperature settings,proportionate rate of mixing, and foam agents to be used for everymaterial.

Heating means and the cooling assembly 26-26A is used to adjusttemperature of molten material 51 to just the right temperature so thatit will have the correct viscosity for foaming when it is in mixingchamber 29A. The cooling assemblies 26 and 26A may thus be formed in twoparts: one a cooling coil, and the other an induction heating coil formore precise control. Both of these units are preferably automaticallycontrolled by thermocouples located in mixing chamber 29A.

The foaming agent, when a gas or compressed air, enters from tank (notshown) through control assembly 56, into manifold 50, thus into nozzle60 wherein it is injected into the molten material 51, thus forming afoamed article 11. Control assembly 56 typically comprises a high speedvalve that controls the flow of air. With certain kinds of nozzles 60 itis desirable to make the valve 56 flutter or pulse in order to make theair intermittent, thus assuring formation of bubbles 52 of controlledsize in the material 51. If an atomizing nozzle 60 is used, a valve willcontrol flow of air to determine the bubble density or frequency.Control assembly 56 will also have the necessary equipment to cool theair if not precooled.

The vertical process shows one nozzle 60 injecting gas or air bubbles 52directly into the mixing chamber 29A and centered under the formingcavity or vertical mold structure 30, 31. The forming cavity and mixingchamber is shown in FIG. 5 as a longitudinal cross-sectional drawing.Therefore nozzle 60 as shown in vertical drawing is one of a row ofnozzles equally spaced along the center of the mixing chamber. Thenumber of nozzles 60 required is determined by the number required todistribute bubbles evenly across the cross section of the foamed article11. Nozzles 60 are insulated from wall of mixing chamber and moltenmaterial 51 except for the tips where air enters the molten mass.

A different style manifold and nozzle assembly can be used in either avertical or horizontal molding embodiment, namely, a plate with manysmall holes or a finely meshed screen permitting gas or air to passthrough it into molten mass. The holes in plate or screen are so smalland the viscosity of the molten mass is so thick that the moltenmaterial will not flow through holes. This plate can be made wider andmounted flush on the bottom of the mixing chamber as in FIG. 8 or bottomside of a horizontal mold arrangement--FIG. 10. For example, it might bean inch wide strip and the length of the mixing chamber and located inthe bottom of the mixing chamber. The manifold, in this case, would be abox like structure with one side being the perforated plate or screen.By having pressure in box higher than pressure in mixing chamber thefoaming agent will be forced into the molten mass 51 in the mixingchamber, thus forming the foamed product 11. This style of nozzle forinjecting foaming agents into mixing chamber may be used to injectgases, liquids or solids. It will work best with gases and liquids, butcan be modified to inject solids so they will come through theperforated plate. Another way that powdered foaming agents can be usedwith this style manifold and nozzle assembly is where the powderedfoaming agent is injected into the manifold at one end and heated to apoint where the powder gives off a gas which then passes throughperforated plate into the mixing chamber. Many of the hydrides, sulfatesand carbonates in powder form may be used to foam materials using themanifold and nozzle assembly described above. This, however, makes itmore difficult to control the amount of gas generated from the powder.

The critical point in making a foamed material is the point ofsolidification or crystallization. The beginning of crystallization isin area of wick 45 and at point where bubbles are spread out. In thisarea and the area just following it the molten mass becomes solidified.Thus the article 11 becomes solid within the first few inches ofpenetration into the mold cavity 30-31. The length of the solidificationarea is determined by temperature of the molten mass, the speed ofwithdrawal of the article 11 and the rate of heat transfer to coolingpipes 40-41.

Similar features are identified by related reference charactersthroughout the remaining embodiments to facilitate comparison. Theunderlined characters represent a general feature, lettered notationrepresents duplicate or alternate features and primed notationrepresents slightly modified features.

The embodiments of FIGS. 6 and 7 illustrate that the article 11' shapemay be varied in a manner helpful to produce construction memberscapable of bearing weight and useful as modular building materialsbecause of the offset longitudinal rib support members 65 thereon. Othershapes likewise may be made by this continual withdrawal process bymodifications to the forming mold structure. This embodiment illustratesthat the pocket forming capability works well in a funnel shaped mixingchamber 66 that permits the semi-hardening material to be drawn into theribs 65 or panel 67 portion of the article 11' to thereby retain theadvantages of the material properties in the skin and the skeletalinterior. It is noted that the manifold 57' is shown of the typehereinbefore described with a screen 68 on equivalent aperture plate onthe bottom of the mixing chamber 66.

The configuration of FIG. 8 shows an embodiment where the molten mass islocally generated by heater coils 70 about the passageway 26' leadinginto the mixing chamber. The molten material is kept under a feedpressure as fed into pipe 71 by means of screw feed 72 rotated by shaft73 to feed granular raw materials 74 from bin 75 into the influence ofheating coils 70. Also shown is means for initiating a run of articlesshown as a slab 76 similar to a produced panel in thickness with anextending anchor 77 which can be inserted into the molten mass andfrozen thereinto to permit withdrawal of the first panel section.

FIG. 9 illustrates means for removing any gases in the molten massbefore entry into the mixing chamber through pipe 26. Any unscheduledbubbles or bubbles of uncontrolled size will deteriorate the product.Other methods of degassing such as shown in the aforesaid U.S. Pat. No.3,960,532 may also be used, if desired.

The molten raw materials 20 are maintained at proper temperature byelectrodes 80, 81 and associated energizing circuits preferablytemperature controlled from heat sensing thermocouples or the like inthe molten materials 20.

The molten materials are passed by channel 82 controlled by gate 83 intothe degassing chamber 86. There the agitator 84 turned by motor 85 in adirection carrying the molten materials upward will serve to accumulateall bubbles and gases in the region 90 above the molten materials 20.

The gage 27' controls gate 89 to assure the proper pressure head of themolten mass 20, and the electrodes 87, 88 will keep the molten masswithin agitator 86 at the proper temperature for flow out of channel 26into the article forming mold assembly such as shown in FIG. 5.

The same procedure of foaming the panels can be done with horizontallydisposed molds 30", 31" as shown in FIG. 10, where long panels notfeasible from a vertical mold are desired, provided that appropriateprecautions are taken. Thus, the bubbles 52' need be inserted from thebottom of channel 92 as shown from nozzles 68' extending from manifold57" along a specified horizontal region so that the bubbles 52' can risethrough the molten mass to the position where it is being hardened.Thus, the rightmost nozzles 68' will provide bubbles 52' near the bottomof the article 11B, while the leftmost nozzles 68' will provide bubblesrising to near the top of the article 11B. In this embodiment a skin canbe prepared on the upper side only if desired and the foamcharacteristics can extend to the bottom of the article 11B.

In order to achieve the necessary bubble dispersion and skincharacteristics the cooling coils 41' on the top cause the moltenmaterial to start hardening near the position 91 where the first nozzle68' can insert bubbles to raise to a position adjacent the upper skin ofthe article 11B. Conversely the lower cooling or cooling-heating coils40' keep the bottom mold member 30" warmer so that hardening does notoccur until after the last nozzle 68' on the right. Thus a uniformdistribution of the bubbles or other foaming agent occurs through thebody of the article 11B even when horizontally moved. It is critical asbefore explained to have the bubbles or pockets formed of uniform sizeand frequency to achieve the desired article properties.

It may thus be seen that the process of this invention comprises amethod of feeding a molten or liquid material preferably through astorage and degassing container to obtain a relatively even controlledflow into a mixing chamber where it is mixed with a foaming agent in theright proportions to make constant sized bubbles of controlled frequencythus making a light but strong article of special properties, which isthen formed into a specific shape and quickly hardened by cooling orcuring. It further comprises several methods of preparing to inject andinjecting a foaming agent be it gas, liquid or solid. It also includes amethod of continuously removing a panel which is continuously inspectedso that marked areas can be cut out. The panel is cut into desiredlengths while continuously being removed.

It further includes a method of continuously casting a foamed materialby means of bottom pouring or bottom injecting of molten or liquidmaterials, alloying or foaming agents into a mold, die or formingdevice. It further includes a means of tempering the skin and internallycooling a casting by pre-cooling injected alloying or foaming materialsand injecting the alloying or foaming materials as close as possible tothe area where the material is to be solidified or crystallized andcontrolling die temperature.

Other novel article and process features believed descriptive of thespirit and nature of this invention are defined with particularity inthe claims.

Industrial Application

An article, which may be a panel of foamed glass or similar material, isformed with a skin which does not deteriorate in the environment andwith a strengthened internal foam structure which will bear weight sothat construction panels and the like can be made with properties whichcan replace most common construction materials and offering many newfeatures, and further the process can be used to make a wide variety ofproducts.

This article is made in a continuous process from molten glass withappropriate control of the foaming process and with tempering of anouter skin to produce a product which will not shatter or crack uponimpact outside the local region of impact.

I claim:
 1. The method of making a foamed article providing uniformdensity and cell size, insulation properties, long life withoutprotective coatings when exposed to the atmosphere, strength andfracture resistance suitable for weight bearing constructionapplications having the properties in combination to achieve theforegoing features comprising,(a) a solid poreless material that ismeltable at high temperatures moldable into predetermined shapes andtemperable in the cooling process, (b) produced in a configurationhaving a solid skin surface of said material of predetermined thicknesstoughened by tempering to withstand impact and to resist shattering ofthe skin over areas outside the impact region, and (c) further having aninterior structural skeleton of said material interconnected in asubstantially non-symmetrical pattern interspersed by a myriad of lowdensity pockets of substantially uniform size wherein the skeletonprovides a bearing weight distribution network that disperses impactshock over widely dispering skeletal paths encompassing the pockets andfurther prevents any common pathway through the body of the object thancan support a fracture line through the object, whereby there is anability of the configuration to absorb shock and impact and to supportsubstantial bearing weight while being light and having substantialinsulating capacity over a long life by introducing means forming thelow density pockets of predetermined substantially constant size intomolten material confined in a mold tempering and forming said skinsurface from the molten material, permitting the pockets to rise throughthe molten material in said mold to a position being cooled and hardenedthereby to form the bubbles in said interior structural skeleton byhardening of the molten material about the pockets, continuously movingthe article through said mold while controlling the mold temperature tocool the skin of the article in a predetermined manner thereby to temperthe outer surfaces of the article, and providing a stream of moltenmaterial from a furnace into said mold to replenish the materialcontinuously withdrawn by said article.
 2. The method of claim 1including the additional steps of orienting the mold vertically,introducing the molten materials into the bottom of the mold andwithdrawing the article upwardly from the mold.
 3. The method of claim 2wherein the pockets are filled with a gas including the additional stepof controlling the pressure of the molten material to have apredetermined pressure above atmospheric at the position being cooledand hardened, thereby to retain gas in said pockets at super atmosphericpressure.
 4. The method of claim 1 including the step of inserting awithdrawing tool into molten material within said mold and moving saidtool with the material hardened thereabout to initiate the continuousmovement of the article through the mold.
 5. The method of claim 1including the step of degasifying the molten material before entry intosaid mold.
 6. The method of claim 1 including the step of introducinggas bubbles at a predetermined size and rate into the molten material torise therein, thereby to establish the low density pockets and foamcharacteristics of said article.
 7. The method of claim 6 including thestep of controlling the temperature of the gas forming the bubbles tointroduce a predetermined cooling effect into the molten material. 8.The method of claim 6 including the step of introducing a selected gasfor said bubbles producing a chemical reaction with the molten materialabout the surface of said bubbles interspersed in the interior of thearticle.
 9. The method of claim 1 including the steps of orienting themold horizontally, establishing over a specified horizontal regioncooler temperatures within the mold at the top than at the bottom tothereby harden the top portion first, and feeding said means forming lowdensity pockets into the molten material at successive positions alongthe specified horizontal region thereby to permit the pockets to risethrough said molten material in a manner producing a substantiallyconstant pocket dispersion through the interior of said article awayfrom the skin.
 10. The method of claim 1 wherein the step of introducingthe low density pockets comprises the insertion of grains of controlledsize of a material that reacts at the temperature of the moltenmaterial.
 11. The method of claim 1 including the step of introducing asubstance forming the low density pockets with the property ofinteracting with the molten material surrounding said pocket to changeits physical characteristics.